Thermal actuator



Nov. 24, 1970 c;. w. DAHL THERMAL ACTUATOR MILL Ai so 2 Sheets-Sheet 1 Filed Oct. 14, 1968 THERMAL ACTUATOR Filed 001;. 14, 1968 v 2 Sheets-Sheet 2 Ina/ere fiem ye United States Patent 3,543,211 THERMAL ACTUATOR George W. Dahl, Warren, R.I., assignor to G. W. Dahl Company, Inc., Bristol, R.I., a corporation of Rhode Island Filed Oct. 14, 1968, Sen No. 767,308 Int. Cl. A62c 37/12; F16k 31/56; H01h 37/76 U.S. Cl. 337-408 6 Claims ABSTRACT OF THE DISCLOSURE In a system wherein a pair of relatively movable members are normally urged to move with respect to each other by relatively heavy spring means, said movement being prevented by a thermal actuator comprising a pair of axially aligned struts which counteract said spring means when in their straight line position, said actuator further comprising means normally bearing on said'struts so as to cause them to collapse from their straight line position wherein said spring automatically becomes effective to cause relative movement of said members, and a fusible link rendering said last named means ineffective until a predetermined temperature is reached sufficient to fuse said link.

BACKGROUND OF THE INVENTION This invention relates generally to temperature responsive mechanisms, and particularly concerns those which are restrained by a fusible element until a threshold temperature is reached which melts the element.

There are many applications calling for mechanisms which remain in a poised condition so long as the ambient temperature stays within a certain range, but which are released to perform a vital function when a particular temperature threshold is reached. Such mechanisms are used, for example, to shut off the flow of fuel or some other combustible fluid, to turn on a fire sprinkler, or to close a fire door when the ambient temperature indicates that a fire hazard may be present.

Conventional mechanisms employed in such applications usually have a biasing spring, the force of which is counteracted by a fusible link. The link functions to resist the force of the biasing spring under normal temperature conditions, but to melt and thus yield to the spring force when a predetermined temperature threshold is reached. It has been found, however, that such links are not completely reliable, particularly where a relatively strong spring force must be counteracted. Specifically, it has been found that these links may inadvertently break, even at ordinary temperatures, since the soft, fusable material of which they are made is not well adapted to wtihstand the strain imposed by a strong biasing spring. It has, therefore, been found desirable to provide a fusible link mechanism in which the link itself is not subjected to the force of the biasing spring.

At least one attempt has been made to design a fuse release mechanism in which the fusible element is not subjected to the force of the operating spring. For example, in FIGS. 1 and 2 of US. Pat. No. 792,343 to R. W. Newton, a temperature responsive automatic sprinkler valve for fire applications is shown employing a bracing mechanism comprising a pair of axially aligned struts. The load exerted on these struts by the storing valve actuating spring is applied in a dead center axial direction, so that the only function which must be performed by the fusible element is to prevent collapse at the knee of the two struts.

The disadvantage of the device shown in the Newton patent is that in the form shown in FIGS. 1 and 2, there are no means for insuring and/or accelerating the collapse of the struts upon fusing of the fusible element thus raising the possibility that the struts might inadvertently remain in their straight line position, counteracting the operating spring, even after fusing of the fusible element. In FIGS. 3-7 Newton shows a spring for hastening collapse of the struts upon fusing of the fusible element, but to do so, the struts are angularly disposed with respect to each other, thus at least partially defeating the basic purpose of the struts, since obviously the struts cannot effectively counteract the operating spring unless they are in straight line relation with respect to each other.

Thus, the design dilemma into which the prior art has fallen may be summarized as follows. To the extent that the thrust of the operating spring is allowed to contribute to the collapse of the restraining linkage at the proper time, the collapsing force exerted thereby must be borne by the fusible element. This is not a reliable or practical situation since where a strong operating spring is in use, the fusible link must be made impractically bulky and strong to effectively counteract the operating spring. Otherwise there is always danger of accidental breakage of the fusible link due to the load applied thereto by the operating spring. FIGS. 3 to 7 of the Newton patent, as previously described, exemplify this type of mechanism, wherein the thrust of the operating spring is at least partially borne by the fusible member. On the other hand, if the fusible element is completely isolated from the thrust of the operating spring, and no additional means are present for insuring collapse of the struts, as in Newtons FIGS. 1 and 2, the collapse of the bracing mecha nism at the appropriate time is left to the laws of probability, which gives something less than reliability under emergency conditions.

SUMMARY OF THE INVENTION This invention aims at resolving the above stated dilemma by providing a dead center axially aligned strut mechanism of the type in which the fusible element does not bear any of the load exerted by the operating spring. However, a relatively weak auxiliary spring is provided which exerts a small collapsing load upon the bracing struts, so as to insure that these struts will buckle at the DESCRIPTION OF THE DRAWINGS In the drawings which illustrate the best mode presently contemplated for carrying out the present invention:

FIG. 1 is an elevational view, with parts broken away and sectioned for clarity of illustration, of an emergency fuel shutoff valve employing the thermal actuator of the instant invention;

FIG. 2 is an enlarged elevational view of the thermal actuator of FIG. 1, with parts broken away and sectioned for clarity of illustration. In FIGS. 1 and 2 the mechanism is shown prior to release;

FIG. 3 is a view similar to that of FIG. 2, but showing the condition of the mechanism at the beginning of thermal release;

FIG. 4 is a view similar to that of FIG. 3, but shows the condition of the mechanism at a time when the process of thermal release is almost completed;

FIG. 5 is similar to FIG. 2, but demonstrates the condition of the mechanism at the start of a manual release opgration, which is an additional feature of this invention; an

FIG. 6 is similar to FIG. 5, but shows the condition of the mechanism at a time subsequent to FIG. when the process of mechanical release has advanced further.

The same reference characters refer to the same elements throughout the several views of the drawing.

DESCRIPTION OF THE INVENTION The thermal actuator of the instant invention will be described in connection with a particular valve 10 which is designed to control a fuel line, although the invention is equally applicable to any other type of valve or mechanism which is required to react promptly in response to a predetermined elevated temperature. The valve 10 comprises a conventional valve body 12 having a sleeve 14 extending therefrom and formed with threads 18 at its upper end. A valve stem 20 is reciprocable between upper and lower limiting positions within the hollow interior of the sleeve 14 as viewed in FIG. 1. At its lower limiting position, as shown in broken lines in FIG. 1, the stem 20 closes the valve 10'. At any position above its lower limit, the valve stem 20 opens the valve 10 in proportion to its displacement. The valve stem 20 has a threaded portion 21 which is threadedly engaged with the interior thread of a reciprocable collar 22, so that the valve stem 20 and collar 22 reciprocate as a unit, for closing and opening the valve 10.

The collar 22 is formed with an upstanding cylindrical extension 24 which serves as a guide for a coil compression spring 26. This is a relatively heavy and strong spring which serves to bias the collar 22 and valve stem 20 downwardly very firmly and rapidly in the event of a fire emergency, to close the valve 10 without delay. The spring bears downwardly against the shoulder formed where the collar 22 projects laterally from the cylindrical extension 24. At its upper end, the valve shutoff spring 26 acts against a fixed yoke 28 the arms of which are notvisible in FIG. 1 because they extend perpendicular from the view shown in FIG. 1.

The yoke 28, at its ends, has a pair of respective vertical rails 30, one of which is seen in the view of FIG. 1, which serve to guide vertical reciprocation of the collar 22, and for this purpose the collar 22 is formed with extensions 32 perpendicular to the plane of the drawing, which slidably engage the vertical rails 30.

At its lower end, the yoke 28 is fixedly connected to unit 36 comprising a hexagonal nut 38, a cylindrical sleeve 40 depending therefrom, and a circular disc 42. The unit 36 and specifically nut 38 has interior threads which are engaged with the threads 18 on sleeve 14, and a hexagonal nut 44 is also threaded on the sleeve 14 below disc 42 to securely lock the latter in proper position on sleeve 14.

A handle 50 is secured to a threaded, reduced tip 52 at the upper end of the valve stem 20 by means of a washer 54 located below the handle and a nut 56 secured above it. In order to effect normal opening or closing of the valve 10, handle 50 is rotated clockwise or counterclockwise respectively, which results in relative movement between stem 20 and collar 22 due to the threaded interconnection therebetween, and due to the fact that collar 22 is held against rotation by engagement of extension 32 in rail 30.

The open position of the valve 10 is shown in full lines in FIG. 1 and in this position the stem 20 is maintained open against the action of spring 26 by means of brace mechanism 60. When, however, said brace mechanism becomes inoperative, spring 26 rapidly causes stem 20 and collar 22 to move as a unit to close valve 10. If it is subsequently desired to reposition the valve to the full line position of FIG. 1, valve stem 20 may either be pulled upwardly against the action of spring 26 or else handle 50 may be rotated counterclockwise to threadedly move collar 22 upwardly with respect to stem 20 until a new brace mechanism can be inserted, after which handle 50 would be rotated clockwise until the valve '10 again assumes the desired open position.

As stated, the valve is ordinarily maintained in its open position (illustrated by the solid lines of FIG. 1) by means of brace mechanism 60 which normally holds the valve open, but releases it when a predetermined threshold temperature is reached. The mechanism 60 accomplishes this by means of a pair of axially aligned struts 62 and 64. Strut 62 has a threaded upper extension 66 formed with a conical point 68 at the upper end thereof. This point 68 is accommodated within a conical recess 70 on the underside of the reciprocable collar 22. The conical recess 70 is shallower than the conical point 68, so that substantially a point contact is made between elements 66 and 22. As a result, under static conditions the compressive force exerted by the valve closing spring 26 can only be transmitted axially to the strut 62.

A similar point contact is made between a conical point 72 at the lower end of strut 62, and a shallower conical recess 74 formed in the lower strut 64. Finally, a similar point contact is made between a conical point 76 at the upper end of an adjusting screw 78 threaded upwardly through the circular member 42, and shallower conical recess 80 at the lower end of strut 64. Each of the point contacts described serves to restrict the transmission of compressive forces by the valve closing spring 26 to a component which is axial through the struts 62 and 64 under static conditions.

The lower strut 64 has an axial extension 82 which is in the form of a half cylinder and which lies alongside and shrouds the upper strut 62. The extension 82, in turn, is formed with a spring-engaging lug 84 extending laterally therefrom. A corresponding spring-engaging member 86 is threadedly engaged with section 66 of the upper strut 62, and also extends laterally therefrom. A pair of confronting shallow circular recesses 88 and 90 are formed on the spring engaging members 84 and 86 respectively, to receive the opposite ends of a weak coil spring 92 held in compression between these recesses on the two members 84 and 86. The function of the spring 92 is to exert a slight movement on the struts 62 and 64 which rotates them about the knee defined by their point contact 72 so that the brace mechanism 60 collapses when the predetermined condition exists at which it is desired to permit closing of valve 10 by means of operating spring 26.

In order to prevent the spring 92 from performing this task prematurely, a fusible link '94 is connected between the members 84 and 86, The link comprises a plate 96 formed with a ring 98 at one end, and a second plate 100 formed with a ring 102 at one of its ends. The two plates 96 and 100 are soldered together in overlying relationship with a material which melts at the predetermined threshold temperature. Below that temperature, the two plates 96 and 100 act as a rigid unit which functions to maintain struts 62 and 64 in axial alignment.

The plate 96 is connected to member 86 by means of a pin 104 which passes through ring 98 and is pushed into engagement with a socket 106 formed in the end of the member 86. In a similar manner, the other plate 100 is connected to element 84- by means of a pin 108 which passes through the ring 102 and is pushed into a socket 110 formed in the end of the element 84. Thus, although the spring 92 attempts to collapse the bracing mechanism 60 by pushing apart the strut extensions 86 and 84, the latter are held together by the link 94 and the pins 104 and 108.

However, when the predetermined threshold tempera-.

ture is reached, and the soldered connection between plates 96 and 100 commences to melt as seen in FIG. 3, these plates separate, thus severing the link 94. The tendency of the extensions 86 and 84 to separate under the urging of the collapsing spring 92 is then no longer opposed, and the bracing mechanism 60 collapses as the expanding spring 92 causes strut 62 to tip about the knee formed by the contact point 72, and strut 64 to rotate clockwise about the knee point 76.

Within an instant the mechanism will have reached the condition illustrated in FIG. 4, where the parts 96 and 160 of the fusible link 94 have separated completely, and the lower part 100 has been rotated by gravity from the broken line position into the depending position shown by the solid lines. The struts 62 and 64 of the bracing mechanism 60 will have been tipped far out of their original axial alignment, and are about to fall completely away from their original position in which they maintained the collar 22 and disc 42 apart, as seen in full lines in FIG. 1. Consequently, the valve closing spring 26 will now be able to force the collar 22 and its associated valve operating stem 20 downwardly to close the valve 10 firmly and rapidly.

It will be appreciated that as soon as the exact axial alignment of the two struts 62 and 64 is disturbed by the collapsing spring 92, the force of the valve closing spring 26 will be increasingly applied to collapse the bracing mechanism 60. This very quickly and positively accelerates the structs 62 and 64 out of the way so that the valve 10 can be rapidly closed (see arrows 11 in FIG. 1). The closed (or lower) positions of the valve stem 20, handle 50, collar 22 and spring 26 are shown by the broken lines in FIG. 1.

On the other hand, until the moment of emergency or predetermined temperature arises, the entire thrust of the valve closing spring 26 is borne by the axially aligned combination of the struts 62 and 64. Moreover, since the thrust is entirely in an axial direction under pre-emergency static conditions, substantially no component of the force exerted by the spring 26 is applied as a force to bend the knee at contact point 72 and thus collapse the bracing mechanism 60. Accordingly, no bending force of the strong spring 26 must be resisted by the fusible link 94, which might be prone to fail if subjected to such severe strain.

But even in the absence of any collapsing force exerted initially by the spring 26, the resulting dead center condition will not allow the struts 62 and 64 to remain fixed in that position under emergency conditions. As soon as the fusing of the link 94 permits, the collapsing spring 92 will flex the knee at the contact point 72, after which complete collapse takes place to shut off the supply of fuel controlled by the valve 10. But the force exerted by the weak collapsing spring 92, and resisted by the fusible link 94 until the moment of emergency arises, is far less than the force exerted by the valve closing spring 26, and is well within the capability of the link 94 to withstand reliably,

The connecting pin 104 is formed with an eye 120 at the outenend thereof, which provides a convenient hitching place for a pull wire 122. The wire permits the bracing mechanism 60 to be released manually when desired, without waiting for the link 94 to fuse and indeed without affecting the integrity of the link 94 in any way. As illustrated in FIG. 5, if the operator detects an emergency condition before the ambient temperature has risen to the point where the link 94 fuses, he can pull wire 122, which withdraws the connecting pin 104 from its socket 106 (arrow 131), and prevents the fusible link 94 from any longer restraining the extension 86 or its associated strut 62. The fusible link 94 then simply swings around its pin 108 and drops intact from the broken line position in FIG. 5 into the solid line position wherein it depends from the connecting pin 108 as shown. When this happens, the bracing mechanism 60 collapses in the same manner disclosed above, and the result is that the valve closes rapidly just as though a thermal release had occurred. This is illustrated in the View of FIG. 6.

In order to retain the connecting pin 104 frictionally within the socket 106 under normal conditions, yet leave it free enough to be easily Withdrawn by means of the pull wire 122, there is provided an O-ring 123 made of rubber or a like material, which is received within a corresponding annular groove 124 near the mouth of socket 106. This ring 123 is compressible to achieve the desired frictional engagement with the connecting pin 104. The connecting pin 108, on the other hand, makes a tight frictional fit directly with the walls of its socket (FIG. 2), since there is no need for its withdrawal.

A number of convenient adjusting features are provided for in the present invention. One of these results from the ability of the lower contact screw 78 (see FIG. 1) to be threaded up or down relative to the disc 42, so that the proper spacing from the collar 22 is obtained for matching the combined lengths of the axially aligned struts 62 and 64. Once the desired position of the screw 78 is obtained, it can be locked against the disc 42 by means of a nut 140.

In order to maintain the desired axial alignment of the struts 62 and 64, it is essential that the spacing between the center lines of the sockets 106 and 110 be equal to the spacing between the centers of the rings 98 and 102 of the fusible link 94. In order to achieve this condition in view of possible tolerance variations in the length of the link 94, the spring engaging extension 86 may be adjusted along the threaded portion 66 of the struct 62 by simply rotating the strut relative to the extension 86 until the desired spacing is achieved. In order to facilitate rotation of strut 62, an opening 65 is provided for receiving a small bar wrench or the like.

For greater stability, the bracing mechanism 60 is permitted to collapse only in one direction, i.e., the direction required by the collapsing force exerted thereon by the spring 92. It is prevented from collapsing in any other direction, by means of the surface of the strut extension 82 and the semi-cylindrical walls 132 and 134 (see FIGS. 2 and 3) which shroud the lower outer end of the strut 62 and prevent it from tipping about the knee formed by the contact point 72. This is advantageous in that it prevents the bracing mechanism from collapsing inwardly toward valve 10, which, if allowed to happen, might possibly interfere with closing movement of the valve.

It will now be appreciated that the present invention provides a greatly improved fusible link mechanism which insures that the valve or other mechanism will be reliably held open under normal conditions, but which also insures 100% fail-safe operation in that the bracing mechanism must collapse and permit closure in the event of a fire emergency. Under such circumstances, the desired closure takes places positively and very rapidly. As previously stated, it is not essential to the underlying spirit of the instant invention that movement of stem 20 operate a valve, but rather movement of this member could perform any function that may be desired upon reaching the predetermined threshold temperature.

Since the foregoing description and drawings are merely illustrative, the scope of protection of the invention has been more broadly stated in the following claims, and these should be liberally interpreted so as to obtain the benefit of all equivalents to which the invention is fairly entitled.

What is claimed is:

1. A temperature-responsive mechanism comprising a pair of members mounted for relative movement with respect to each other, first load means normally urging said members to move relatively, a brace mechanism counteracting said first means until a threshold temperature is reached, said brace mechanism comprising a pair of axially aligned strut members, means mounting said strut members so that they counteract said first load means without any collapsing torque being exerted on said strut members, second load means carried by said strut members and normally imparting a collapsing torque thereto, said second load means being relatively weak compared to said first load means, and fusible means carried by 7 r r said strut members counteracting said second load means, said fusible means being rendered inoperative when a temperature is reached sufficient to fuse said fusible means, each of said strut members having an extension extending laterally therefrom, said second load means comprising a spring mounted under compression between said extensions, said fusible means comprising a link connected to and extending between said extensions, said link having an intermediate fusible portion, one of said extensions being adjustable along the length of its respective strut member.

2. In the mechanism of claim 1, means carried by one of said strut members for permitting collapse of said members in one direction only.

3. In the mechanism of claim 2, wherein said last mentioned means comprises a semi-cylindrical shroud carried by one of said strut members, said shroud encircling approximately half the circumference of a portion of the other strut member, whereby upon collapse of the strut members the joint therebetween is forced to move latera1- ly in the direction of the shroud.

4. In the mechanism of claim 3, wherein said shroud is located on the opposite side of its strut with respect to said movable members, whereby collapse of said struts will be in a direction away from said movable members.

5. A temperature-responsive mechanism comprising a pair of members mounted for relative movement with respect to each other, first load means normally urging said members to move relatively, a brace mechanism counteracting said first means until a threshold temperature is reached, said brace mechanism comprising a pair of axially aligned strut members, means mounting said strut members so that they counteract said first load means without any collapsing torque being exerted on said strut members, second load means carried by said strut members and normally imparting a collapsing torque thereto, said second load means being relatively weak compared to said first load means, and fusible means carried by said strut members counteracting said second load means, said fusible means being rendered inoperative when a temperature is reached sufiicient to fuse said fusible means, each of said strut members having an extension extending laterally therefrom, said second load means comprising a spring mounted under compression between said extensions, said fusible means comprising a link connected to and extending between said extensions, said link having an intermediate fusible portion, said link further having ring-like portions at its opposite ends, pin means extending from said extensions freely receiving said portions therearound whereby to mount said link with respect to said struts.

6. In the mechanism of claim 5, wherein one of said pin means is readily removable from its extension where by to provide a manual release from said link.

References Cited UNITED STATES PATENTS 3,180,524 4/1965 Shepard et al 337-411 X 2,272,857 2/1942 Vonich 169-38 792,343 6/1905 Newton 16939 FOREIGN PATENTS 858,231 1/1961 Great Britain.

BERNARD A. GILHEANY, Primary Examiner D. M. MORGAN, Assistant Examiner US. Cl. X.R. 

